Drawing apparatus



April 1958 E. L. DARGUE 2,832,144

DRAWING APPARATUS Q Filed Feb. 5. 1955 1 All r111 rtr'nT-T' Attorney United States Patent DRAWING APPARATUS Eric Lewin Dargue, Halifax, England Application February 3, 1955, Serial No. 485,850 3 Claims. (Cl. 33-102) This invention relates to drawing apparatus of the type wherein a drawing board is provided with a parallel straight edge adapted to slide over the surface of the board.

Whilst the invention may be adapted to drawing boards of any size it is particularly applicable to the smaller sizes of drawing board, which are intended to be portable.

The object of this invention is to provide a protractor head and one or more scaled straight edges which may be used inconjunction with the parallel straight edge.

It is known to provide a drawing board with a parallel straight edge and a protractor head slidably fixed to the parallel straight edge.

According to this invention a protractor head for use with a parallel straight edge is provided with a slide portion adapted to be connected to a straight edge and having resilient means incorporated in its construction, the resilient means being adapted to bear against one edge of the straight edge.

Preferably the slide portion is so constructed that there are provided three or more bearing surfaces for engaging the two edges of the straight edge. This is preferably achieved by forming two bearing pads on one side of the slide and fixing one or more leaf springs in the other side of the slide, the leaf springs being curved so that one point of them bears against the opposite edge of the straight edge to the two bearing pads. Alternatively there could be provided a single bearing pad on one side of the slide and two leaf springs, or a single leaf spring having two convex surfaces adapted to bear on the opposite edge of the straight edge to the bearing pad.

The leaf springs may be adjustably mounted in the slide portion of the protractor head.

The leaf springs are preferably mounted on a movable member supported by the slide portion.

The movable member is retained in position on the slide portion preferably by means of a spring-loaded member.

This construction enables the protractor head to be readily detached from the straight edge and readily attached in the correctly aligned position, without any adjustment.

The protractor head may be of a known construction having two scaled straight edges disposed at 90 to each other and may be provided with means for adjusting the position of the straight edges.

The invention will now be particularly described with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic plan view of a protractor head constructed in accordance with the invention;

Figure 2 is a diagrammatic plan view of an alternative type of protractor head in accordance with the invention;

Figure 3 is an enlarged view on line AA in Figure 2;

Figure 4 is an enlarged view on line BB in Figure 2;

Figure 5 is an enlarged diagrammatic view showing the resilient means.

As shown in Figure 1, a drawing board 1 is provided with a parallel straight edge 3 made from celluloid or similar transparent material. Mounted on the parallel straight edge 3 is a slide 5 which is provided with two bearing pads 7 which engage the top side of the straight edge and two leaf springs 9 which engage the bottom side of the straight edge, the leaf springs 9 operating on the straight edge 3 in substantially the same manner as the cursor spring of a slide rule.

The upper end of the slide 5 is semi-circular when viewed in plan and has inscribed thereon a 90 right angle which is sub-divided into degrees in the form of a protractor. The top of the slide also has cut therein a slot 11 which forms a right angle and into which extends a screwed stud 12 mounted on a protractor head 13, here inafter referred to.

The protractor head 13 is pivotally connected to the semi-circular top of the slide, on a pivot 16, and each leg- 17 thereof is suitably sealed in a predetermined manner. The screwed stud 12 mounted on the protractor head 13 extends through the slot 11 and has mounted on its protruding end a thumb screw 15 by means of which the head 13 may be locked in a predetermined position which is de- '3 cided by placing an indicating line, not shown in the accompanying drawings, marked on the vertical leg 17 of the head 13 in line with the required angle which is shown on the slide top.

When employing the above described means of attaching the slide 5 to the straight edge 3 it is readily attached and detached.

In an alternative type of protractor head as shown in Figure 2 of the accompanying drawings the slide 5 is mounted on a straight edge 3 as previously described, having bearing pads '7 adapted to bear on the straight edge also as previously described. A protractor head 13, as previously described, is connected to the top of the slide.

Formed in the lower portion of the slide 5 are two vertically extending slots 19 through which extends screws 21. Supported by the screws, on the portion which protrudes from the back face of the slide, is a member 23 on which are mounted two leaf springs 9.

Mounted in each end of the member 23 is a peg 25 which is adapted to register with any one of a series of depressions 27 formed in the slide 5 parallel with the slots 19. Disposed between the head of the screw 21 and the front face of the slide 5 is a spring 29 which acts on the head of the screw and retains the pegs 25 in the depression 27, thereby retaining the member 23 in a fixed position.

Thus, when employing the above described protractor head, it is found that the distance between the member 23 and the bearing pads 7 is larger or smaller than the width of the straight edge 3, pressure is applied to the head of the screws 21 thereby compressing the spring and removing the peg 25 from the depression 27.

When the above described operation has been carried out the member 23 is moved until the peg 25 enters the appropriate depression. When this occurs the pressure is removed from the screw and the peg is retained in the new position by the spring. The previously described function is repeated on the second screw and the position of the member 23 thus altered to correspond to the width of the straight edge.

The protractor head is thus ready for mounting on the straight edge where it is retained thereon by the leaf springs 9.

It will be appreciated that, whilst in the above described arrangements, two leaf springs have been employed one, only, may be used.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A protractor for use with a parallel straight edge, comprising a slide member, at least one fixed bearing surface and at least one resilient bearing surface, an adjustable member carrying at least one of said bearing surfaces, the other bearing surface being carried by said slide member, means mounting said adjustable member on said slide member for adjustment relative thereto, said means comprising a locating element mounted on one of said members and the other of said members having a series of recesses therein, resilient means urging said locating element towards said recesses, and manually operable pressure means opposed to said resilient means For releasing said locating element from said recesses.

2. A protractor for use with a parallel straight edge comprising a slide member, at least one fixed bearing surface, and at least one resilient bearing surface, an adjustable member carrying at least one of said bearing surfaces, the other bearing surface being carried by said slide member, means mounting said adjustable member on said slide member for adjustment relative to said slide member, said means comprising a locating element mounted on one of said members and the other of said members having a series of recesses and a slot therein, said adjustable mem her having a screw-threaded hole therein, a headed screw projecting through the slot in said member having said series of recesses and engaging in said screw-threaded hole, and a compression spring surrounding said screw and disposed between said member having said series of recesses and the head of said screw.

3. A protractor for use with a parallel straight edge,

comprising a slide member, two fixed bearing surfaces fixed to said slide member, an adjustable member mounted on said slide member for adjustment relative thereto, said adjustable member carrying at least one resilient bearing surface, the slide member having a series of locating recesses in one face thereof and having a slot therein, a locating element fixed to and projecting from one face of said adjustable member for engagement with any one of said series of recesses, said adjustable member having a screw-threaded hole therein, a headed screw projecting through the slot in said slide member and engaging in said screw-threaded hole, and a compression spring surrounding said screw and disposed between said slide member and the head of said screw.

References Cited in the file of this patent UNITED STATES PATENTS 

